Can you poll a pipe?

[Eric Gisin]

The ability to poll pipes and ttys is an extension by Interactive (ISC),
and is documented in the manual. select (in libinet) just calls poll.
I understand SCO UNIX added a separate select system call, which
has the ability to check file descriptor that poll can't.
I don't know what ESIX does, since they don't have socket emulation.

I would think that anyone who ports the BSD rsh to SysV would have
to provide poll or select on pipes, otherwise you could not use rsh in pipelines.